1. Field of the Invention:
The present invention relates to a fullerene-derived metallocene, and more particularly to a fullerene-derived metallocene suitable for use as a catalyst for preparing olefin polymers.
2. Description of the Prior Art:
Polyolefins have been synthesized by Ziegler-Natta catalysts for over three decades. This chemistry has evolved into a major industrial process which involves an intensive catalytic coordination chemistry of transition metal complexes. Enormous variations of transition metal-derived catalyst systems have thus been developed for these purposes. The ongoing trend of producing new polyolefins requires a better control of the molecular structure and molecular weight of resulting polyolefins.
Over the past few years, increasing amounts of research on the utility of metallocene catalysts in the polymerization of olefins, especially .alpha.-olefins, have progressively replaced the development of Ziegler-Natta-related chemistry. Advantages of the metallocene catalyst application include the versatility of these catalysts in regulating the tacticity of the polymer formed and the increased activity of these catalysts towards higher .alpha.-olefins as compared with traditional Ziegler-Natta catalysts.
Fullerenes are a class of carbon molecule having an even number of carbon atoms arranged in the form of a closed hollow cage, typically spheroid, wherein the carbon-carbon bonds define a polyhedral structure.
Several functionalized fullerene derivatives have been reported. For example, fullerenes with relatively small functional groups or addends such as amido, alkoxy, and halides have been described. See, e.g., U.S. Pat. No. 5,177,248; European Application No. 546,718 (treatment of unfunctionalized fullerenes with trifluoromethanesulfonic acid and nucleophiles to form alkoxylated fullerenes); European Application No. 575,129 (treatment of unfunctionalized fullerenes with sulfuric acid to form sulfated fullerenes). Macromolecules have also been reported to attach fullerenes. For example, U.S. Pat. No. 5,635,581 discloses a fullerene polymer which includes a fullerene core and a plurality of prepolymer units.
However, until now, no one has ever disclosed attaching metallocenes to a fullerene core.